Field of Invention
This invention relates to a device in the field of vacuum robot, and specifically to a static vacuum shafting device for an integrated rotary transformer.
Description of Related Arts
For rapid development of large-scaled integrated circuit industry, its main technique is in transition from Φ 300 mm, 65 nm to Φ 450 mm, 32 nm. The practice has proven that, many front-end technologies for 0.35 μm or below must be conducted under the ultra-high clean vacuum environment, such as ion implantation, corrosion, coating, deposition, and sputtering. To improve the cleanliness and production efficiency, and reduce the cost, cluster tool has become a main development stream for front-end device of semiconductor. The vacuum robot is the core part of wafers in the integrated circuit device to transmit among various reaction chambers. Because the vacuum robot needs to operate under the vacuum environment, sealing isolation and power transmission between atmospheric and vacuum environment are a technical bottleneck restricting the performance improvement of vacuum robot. The motor shafting and displacement measurement device thereof are the core part of vacuum robot, thus dealing with the vacuum isolation between motor and displacement measurement component properly becomes the core technique to design a vacuum robot shafting.
The critical difference between atmospheric and vacuum robot relies in the power transmission. The atmospheric robot can directly install the motor at the joint position to drive arms. However, arms of the vacuum robot must be operated under a high-vacuum high-cleanness environment. If the motor is directly connected to the arms as well, particles and gases released by the plastic insulation materials on the lateral surface of a motor stator under a vacuum environment will damage the high-vacuum high-cleanness environment. In addition, the copper loss (heat work) to drive the motor directly is relatively large, and is hard to achieve heat dissipation under a vacuum environment, so the motor stator must be installed in the atmospheric environment. On these grounds, how to transmit the motor power from atmospheric environment to the robotic arms under a vacuum environment becomes a bottleneck for the research and development of vacuum robot.
The common vacuum mechanical arm shafting usually realizes static sealing though magnetic couplings, but it also has the following disadvantages. Firstly, in a vacuum environment, the shafting needs special lubrication to reduce the pollution released to the vacuum environment by particles. Secondly, permanent magnet and glue will bring some gas leaks under a vacuum environment. Thirdly, there are gaps between the motor stator and rotor, as well as active magnetic coupling rotor and follow-up rotor, bringing complexity to system control and reducing the system rigidity.
The position detection component is usually required in the shafting system, by which the position and speed of the motor rotor can be measured in real time, and thus to achieve the high accuracy control over the speed, torque, position and good performance.
As an electromagnetic transducer, the rotary transformer is a small alternating-current motor for testing angles in essence, which is used to test shaft angle displacement and angular speed of rotary objects. The structure is very simple, which only has stator, and rotor and no electronic components inside. With the increasing demand on electronical automation control, motor with rotary transformer for rotary shafting becomes a common component.
However, the motor used for vacuum robot shafting is relatively large on weight and space, and the interference by motor bearing and rotor of rotary transformer will result in difficult arrangement in space. At the same time, due to the space limit, the distance between the rotary transformer and other parts is relatively narrow, bringing larger difficulties in design, manufacture, and repair. Besides, because the vacuum isolation between the motor and a displacement measurement device cannot be solved, the rotary transformer is seldom employed as the displacement measurement device for shafting in the vacuum shafting.